surging idle...

my 94 Z34 when idling is surging. i believe it is a vacuum leak. what would you suggest looking at first? no the check engine light is not on, yes it surges worse when the brake is applied at like a stop sign or light, yes it sometimes does not surge, no i cant hear any vac leaks(engine/filter/exhaust is too loud) and no i havent been able to pull codes yet. thanx for your help!

I use a hemostat to pinch off the vacuum lines one at a time to check for leaks. If that doesn't show me anything, I'll start spraying carb cleaner around the throttle body, intake manifold, EGR, etc. and see if the idle straightens out as it is pulled through the leak.